Electrical receiving or repeating apparatus and method of operating the same



May 1, 1923. 1,453,982

B. W. KENDALL ELECTRICAL RECEIVING 0R REPEATING APPARATUS AND METHOD OF OPERATING THE SAME Original Filed Sept 13, 1915 Patented May 1. 1923.

UNITED STATES PATENT OFFICE.

BURTON W. KENDALL, OF NEW YORK. N. Y., ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

ELECTRICAL RECEIVING OR REPEATING APPARATUS AND METHOD OF OPERATING THE SAME.

To all whom it may concern Be it known that I, Bmrron humus hENDALL, a citizen of the United States, residing at- New York. in the county of New York and State of New York, have invented certain new and useful Improvements in Electrical Receiving or Repeating Apparatus and Methods of Operating the Same, of which the following is a. full, clear, concise, and exact description.

This invention relates to electrical receiving or repeating apparatus, and the application is a continuation of my application Serial No. 50,396, tiled September 13, 191:).

A particular application 0tthe invention is to receiving apparatus or repeaters for submarine cables or similar conductors. in connection with which it will he described. ()ne of the objects of this invention is to improve the quality of transmission of signals from an incoming lineto an outgoing line through an amplifier or repeater. Another object is, in this case. to amplify and repeat messagcs from an incoming cable to an outgoing cable while permitting duplex operation of said cables. A further object is to receive and amplify incoming signals with fidelity so that the recorded signals shall he enlarged and faithful copies of the signal wave-forms.

These objects are accomplished by inscrting a transformer wluding into the (!lI cuit from which signals are to lie received connecting another winding of the transformer to an electrical network of special form. to he more particularly described later. amplifying the power appearing in one branch of this net work, and transferring it to an instrument or circuit in which it is to be utilized. The advantages secured by this invention and the dilliculties which are overcome'will he better understood after a brief explanation of the operation of duplex cables. reference being made to the drawings.

In these drawings, Fig. 1 shows the circuit arrangement of two duplex cables terminating in a repeater station: and Fig. 2 shows a modified form of the invention.

Referring to Fig. 1, the reference nu- This application filed February nerals 4 and 5 represent two cables, and it is desired to send signals from the station 7 to the station 8, making use of a relay between the terminals of the cables 4 and 5 in such amanner as to permit of duplex operation. At the terminals of the cable 4 there are two artificial cables 10 and 11 arranged to have characteristics similar respectively to those of the actual cable. At the station 7 there are.connected, between the cable 4 and the artificial cable 10, the two condensers 12 and 13, across which is bridged in the usual manner some indicating instrument 14. The opposite terminal of the cable 4 likewise has the usual con- (lensers l6 and 17, across which would ordinarily be connected some indicating instrument in the same manner as at the station 7. When a signal is sent from the station 7 by the operation of the key 18 in series with the grounded battery 19, an impulse is sent over the cable 4 and the artilicial cable 10, and the circuit is so balanced that there is no potential difference between the points 21 and 22. A potential dillcrcnce is, however, created between the points 24 and 23 at the further end of the cable. 4, and this potential difference would, in general be used to operate an indicating instrument in a manner which is well-known in connection with such duplex operation.

An impulse impressed across the points 28, 25) and coming from any source such as a battery with a kc v or from the output circuit of a relay, as indicated in this figure, will produce a current which divides equally between the paths 4 and 11 of equal impedance. and because of this symmetry, there is for such a signal or impulse no difference of potential between the points 24 and 25, across which a receiving instrument might be connected. Such a receiving instrument will, therefore, not be influenced by signals impressed between the points 28 and 29.

Cable 5 with its artificial cables has the same characteristics as cable 4 with its artificial. cables. If now it is desired to relay a message from cable 4 to cable 5, it will be necessary to connect. through an amplifier, the receiving terminals 24, 25 of the first cable with the transmitting terminals 30, 31 of the second cable, and similarly to connect the receiving terminals 33, 34 with the transmitting terminals 28, 29.

It has been found that an ordlna relay or mechanical amplifier is not suita le for this class of work but that a thermionic amplifier of the audion type may be made to operate very efliciently. Such amplifiers have been used extensively in telephony, and are now well-known in the art. This type of amplifier consists of an evacuated vessel in which are contained three electrodes, a hot electron-emittin cathode, a cool anode and an auxiliary e ectrode usually located-between the anode and the cathode. The auxiliary electrode and the cathode, constituting the in ut terminals of the amplifier, are connects to the circuit the power of which is to be amplified, and the cathode with the cool electrode or plate, constituting the out ut terminals 0 the amplifier, is connecte to the output circuit in which the amplified power is to'appear.

When a voltage is impressed upon the input circuit of such an amplifier, its effect is to vary the strength of the thermionic current which flows between the hotcathode and the cool anode or plate, and since the variations of this current, whose source is a battery in the output circuit, represent larger amounts of power than those required to produce the variations, the device acts as an amplifier. Furthermore, the current in the output circuit of such an amplifier depends only upon the voltage impressed upon its input terminals, the input clrcuit itself havin a very high impedance, and, therefore, ta ing practically no current and acting as an open circuit. Any variations in the input voltage Will be faithfully reproduced as corresponding variations in the output current.

An important feature of a thermionic amplifier is that its input and output circuits have one point in common namely, the connection to the hot cathode, so that there is an electrical connection between the two circuits. In using the amplifier as described in connection with the problem of repeating cable messages, there will, therefore, be an electrical connection between the receiving terminals of one cable and the transmitting terminals of the other into which the signals are to be relayed. Examination of Fig. 1 will show that when such a connection exists, that is, when the input terminals of a thermionic amplifier are connected directly to the receiving terminals 24, 25 or 33, 34, the artificial lines will be shunted, and their usefulness, therefore, destroyed. In this case duplex operation can not be maintained.

One method of eliminating the circuit mnnection just noted would be to connect one winding of a transformer across each pair of receiving terminals, one of these trans formers being shown as 36 in Fig. 1, and to connect the other winding to the input terminals of the amplifier. The output terminals of the amplifier would then be connected to the transmitting terminals such as 30, 31 of the other cable.

The simple method, however, is open to a serious objection, for the voltage induced in the secondary of the transformer is not proportional to the current in the primer but is proportional to the rate at which thi primary current changes, that is, a volta e is present in the secondary only when t e current in the primary is actuall changing. It will, therefore, be clear that t e repeated current will not be a faithful copy of that of the incoming signal but will appear only when the incomin current is changing. To overcome this di culty, that is, to make the voltageover the input terminals a copy of the current to be repeated, is the object of the network comprising resistance 37 and condenser 38 whose design and operation are now to be described.

As mentioned above, the electromotive force induced .in the secondary of the transformer 36 is proportional to the rate at which the primary current changes, that is,

it is proportional to the time derivative of the primary current, and the transformer may, therefore, be spoken of as a difi'erentiating device. In this invention advantage is taken of the fact that a condenser acts as an integrating device, for the potential difference across the terminals of a condenser placed in such a circuit as shown is proportional to the total quantity of electricity which has passed therethrough, and is, there fore, proportional to the time integral of the current flowing in such a circuit.

If the signal coming in from the cable and passing through the primary of the transformer 36 were a pure sine-Wave, the arrangement of the circuit would be very simple, requiring merely a condenser bridged across the secondary of the transformer. In this case then voltage across the terminals of the condenser would be proportional to the time integral of the secondary current, which current would be proportional to the electromotive force induced in this secondary circuit, and which electromotive force in turn is proportional to the time derivative of a primary current. In other words, the voltage across the terminals of the condenser would be proportional to the primary current.

However, the signaling impulses coming in over the cable and causing a current to flow through the primary are complex in character, and are made up, in general, of. a fundamental frequency with a large number of harmonics su erposed, and the secondary circuit containing the inductance of the transformer and the capacity of the condenser 'Jtutlltl behave dilierently to the harmonics f diti'ercnt frequencies, A great distortion would therefore result in the secondary current. and it would no longer be proportional to the clcctromotivc force induced in the 5 i'(t )lltl2ll' of the transformer. It is, therefore, necessary to so arrange the secondary circuitmas to diminish this distortion and cause this circuit to behave similarly for all frequencies impressed thereupon. In other words. this circuit must be so arranged that the current flowing therein shall be substantially proportional to the eleetromotive force imluccd in the secondary. Inasmuch as the distortion of the current is due to the presence of inductance and capacity in the circuit. and in view of the fact that a pure resistance produces no distortion, the desired result may be obtained by making the secondary circuit containing the capacity 38 aperiodic, that is,byintroducing a resistance 37 of such a large value that the distorting effect due to the inductanceand capacity is negligible. In this case the current flowing through the secondary circuit will depend solely upon the resistance 37, which behaved similarly to impulses of all frequencies. The current then being proportional to the in-- duced clcctromotive force will-build up a voltage across the terminals of the condenser which is proportional to the primary current. It a thermionic amplifier 40 is then connected. as shown in the Fig. 1, with its in put circuit across the terminals of a con-- denser 39. the variations in its output current will be proportional to the input voltagc and approximately proportional to the current in the primary of the transformer 26. t

The output circuit of the amplifier 40 is connected. preferably through a condenser 41, to the transmitting terminals 30, 31 of the cable 5. In order to allow the necessary flow oF direct current, a choke coil 42 is connected across the output terminals of the amplifier.

In pra tice the following arrangement and dimensions of elements have been found to be very satisfactory: the transformer 30 is arranged to step up the voltage of the incoming signal. for example. to ten times its original value. Its secondary is connecttul to resistance 37 and condenser 39 as shown. In order to reduce the distortion of the incoming signal to a sufliciently small quantity. the resistance 37 should he in the neighborhood of ten times the resistance of the cable as viewed from the secondary side ot the transformer 36. that is. it should be about. ten times the resistance of the table multiplied by the square of the ratio of turns in the transformer 36. for example. it should he in the neighborhood of 300.000 ohms. The condenser 38 should then be of such a size that the impedance which it. oil'crs to low frequency. say live cycles per second, shall be small compared to the impedance offered by resistance 3?. that is. it should have a capacity in the neighborhood of one microfarad.

In addition to the circuit as described, it may be desirable under some conditions to use a, resistance 44 bridged across the condenser. This resistance is primarily intended to serve as a leak between the grid and filament of the amplifier 40. This resistance should be an exceedingly high one, say of the order of one or two megohms in order that it shall not act as a substantial short-circuit of the condenser 38 and thereby prevent a building up of the desired voltage in the condenser 38. In the circuit, asshown in Fig. 1, this resistance is not absolutely necessary for a conductive path from the filament to the grid as afforded through the secondary of the transformer 36 and the resistance 37. If this resistance 44 is large it will be apparent that the current flowing therethrough will be proportional to the voltage across the condenser 38. and will. therefore. be proportional to the current through primary of the transformer 36.

The function of the condenser 38 and the resistance 37 has beengiven a physical explanation above. The correctness of the conclusions may be briefly verified mathematically as follows:

If M is the mutual inductance between the primary and secondary windings of the transformer 36, and it I is the current flowing through the primary, then the electromotive force induced in the secondary is given by D If L, C and R represent the inductance, the capacity and the resistance respectively of the secondary circuit and times the frequency of impulses. then the current I flowing through secondary circuit will be given by It now the resistance R is made very large compared with the terms ]':I1: and 17%. than in other words. the sccomlary current is proportional to the induced clcctrcuiotivc Force. and is independent oi the frequencies of the induced impulses.

The total quantity ol electricity nhich flows through condenser 38 will be given by the time integral of the current 1,, that is,

.plify the voltage from is the capacity of the condenser and V is the potential difference across Its terminals,

therefore d Q Id} e t V c o so Therefore MI V m From this last it will be seen that the voltage across the condenser 38 is proportional to the current in the primary circuit. It is of interest to note further from the equation for I that, as is to be expected, the capacity reactance of the condenser 38 tends to neutralize the inductance reactance of the transformer, and the resistance necessary to prevent distortion is therefore smaller than would otherwise be necessary.

To secure transmission from cable 5 to cable 4 an exactly similar arrangement of circuits is made to connect the receiving terminals 33, 34 of the cable 5 with the transmitting terminals 28, 29 of the cable 4. By this arrangement it is possible to secure amplification on signals in both directions and also to preserve the property of duplex operation.

Fig. 2 shows a somewhat more eflicient form of the invention. It differs from Fig. 1 in that a second amplifier 48 is used to amthe secondary of the transformer 36. To provide for the flow of direct current in the output circuit of this amplifier, resistance 49 is added, and to restrict the direct current to this circuit a large condenser 50 is connected as shown. The resistance of 49 should be several thousand ohms. The resistance 44, which may be omitted in the circuit of Fi 1, is essential in Fig. 2 for it will be 0 served that there is otherwise no conductive path between the filament and grid of the ampli fier 40, and there is, therefore, no opportunit for the dissipation of charges which may ave accumulated on the grid. As indicated in connection with Fig. 1, this re sistance should be of a very high value in order that it shall produce a negligible effect upon the voltage of a condenser 38.

It has been found also that the insertion of this second amplifier 48 permits the use of a larger transformer 36, which is of advantage in receiving signals of low frequency. In all other respects this circuit arrangement is similar to that shown in the first figure.

The limitation local or localized applying to means or devices recited in the following claims, is to be construed as to exclude the construction of the means or device as meaning a line or conductor extending between stations or points located in difi'erent parts of a city, county or State; that is, extending between stations or points geo aphically remote.

hat is claimed is:

1. The combination of a circuit, a transformer having its primary included therein, an aperiodic circuit associated with the secondary of said transformer, said aperiodic circuit being symmetrically conducting in both directions, a thermionic amplifier and means for associating said amplifier with said aperiodic circuit, whereby power in said aperiodic circuit is reproduced in augmented form. I

2. In combination an electric circuit, an aperiodic circuit, an inductive coupling between said circuits comprising an inductance element said aperiodic circuit being symmetrically conducting in both directions, a thermionic amplifier, and means for associating said amplifier with said aperiodic circuit whereby power in said aperiodic circuit is reproduced in augmented form.

3. The combination of a line, receivin apparatus for receiving signals from sai line. a symmetrically conducting aperiodic circuit located between said apparatus and said line, a transformer having a winding included in said line, said aperiodic circuit comprising a second winding of said transformer, a high resistance and a condenser.

4. In combination with two duplex cables each having separate transmitting terminals and receiiing terminals, a thermionic amplifier and ureans comprising a symmetrically conducting aperiodic circuit between the receiving terminals of one of said cables and said amplifier whereby the signaling currents in said cable are accurately reproduced in augmented form by said amplifier.

5. The combination of a circuit, a transformer having a winding included therein, an aperiodic circuit comprising a second winding of said transformer, a high resistance and a condenser, and a voltage operated amplifier, having input and output terminals, said input terminals being connected with said aperiodic circuit, whereby the voltage appearing over a part of said aperiodic circuit produces a current in the output circuit of said amplifier.

6. The combination of a circuit, a transformer having a winding included therein, an aperiodic circuit comprisin a second winding of said transformer, a igh resistance and a condenser, and a voltage operated amplifier having input and output terminals, said input terminals being connected across the terminals of said condenser, whereby the voltage appearing over said condenser produces a current in the output circuit of said amplifier.

7. In combination with two duplex cables, each having separate receiving terminals and transmitting terminals, an inductive amplifying couplin between the receiving terminals of one on 1e and the transmitting terminals of the other cable, said coupling including a transformer, a thermionic amplifier and an aperiodic circuit.

8. In combination with two duplex cables, each having separated transmitting terminals and receiving terminals, at -ansformer whose primary winding is connected Wltll the receiving terminals of one ot said cables, an aperiodic circuit connected to a second winding of said transformer, means tor amphfying the power of said aper odic circuit, and means for impresslng said amplified power upon the transmitting terminals of the other of said cables.

9. In combination with two duplex cables, each having a pair of transmitting terminals and a pair of receiving terminals, an aperiodic circuit, a transformer 1uductively connecting said aperiodic. circuit with the receiving terminals of one of said cables. a. thermionic amplifier for augmenting the power of said aperiodic circuit. and means for impressing said augmented power upon the transmitting terminals of the other of said cables.

10. In con'ibination with two duplex cables, each having separate transmitting and receiving terminals, a thermionic amphtier having an input circuit and an output circuit, and a transformer, said input circuit containing a resistance, a capacity and second windin of said transformer, said output circuit being connected to the transmitting terminals of one of said cables, the receiving terminals of the other of said cables being inductively related to said input circuit by means of the transformer.

11. In combination with two duplex cables, each having separate transmitting terminals and receiving terminals, a transformer whose primary winding is connected with the receiving terminals of one of said cables, an aperiodic circuit comprising the secondary winding of said transformer, a capacity and a high resistance. means for amplifying the power in said aperiodic circult. and means for impressing said amplified power upon the transmitting terminals of the other of said cables.

12. The combination of a symmetrically conducting aperiodic circuit comprising a capacity, a vacuum tube having input terminals and an output circuit. and connections between said aperiodic circuit and said input terminals.

13. An incoming line. a thermionic amplifier, means comprising a symmetrically conducting aperiodic circuit containiug :1 capacity and being connected between said line and said amplifier whereby the currents in said line are adapted to be accurately reproduced in augment d f 14. The combination of aline, a transformer havin a winding included therein and an aperiodic circuit comprising a second winding of said transformer, a high resistance, and a condenser, the condenser being effectively in shunt to said line, and a thermionic amplifier associated with said aperiodic circuit.

15. An aperiodic. circuit containing in series an inductance, a non-inductive resistance element and a condenser, and a vacuum tube having input terminals and an output circuit, said input terminals bein connected across the terminals of sai condenser.

16. An aperiodic circuit containing in series an inductance, a non-inductive resist ance element and a condenser, a vacuum tube having input terminals and an output circuit. said input terminals being associated with said first circuit, and connecting lead wires individual to each of said circuits, whereby circuit connections for apparatus included in one of said circuits are completed independently of the circuit connections for apparatus included in the other of said circuits.

1?. A two-way repeating system comprising a path for repeating in one direction, a path for repeating in the opposite direction. each of said paths comprising a vacuum tube having input terminals and an output circuit and an aperiodic circuit containing in series an inductance, a noninductivo resistance element. and a condenser, and connecting lead wires individual to each of said circuits whereby circuit connections for apparatus included in one of said circuits are completed independently ot the circuit connections for apparatus included in the other of said cir cuits.

18. The combination of a circuit. a transformer having a winding included therein. and a symmetrically conducting aperiodic circuit comprising a second winding of said transformer, a high resistance and a condenser, said resistance and said condenser having values directly dependent upon the electrical characteristics of the said transformer.

19. An incoming line, a resistance and a condenser in series and associated with said l ne, said condenser being in shunt to said line. and a vacuum tube, said tube repeatmg in substantially the same form current waves impressed thereon. said tube having its input terminals directly' connected across the terminals of said condenser.

20. An incoming line. a corrective network comprising a resistance and a condenser in series and associated with said l ne, said condenser being in shunt to said hue, and a vacuum-tube which repeats in substantially the same form current waves impressed thereon, said tube being res onsive to the drop of potential across the p ates of said condenser.

21.'A receiving system for signals comprisin a line and a correcting network, said line having two side wires, said network being composed of ohmic resistance and condensive reactance and being substantially free from inductive reactance, said resistance being in series with said line, said condensive reactance being connected in shunt to said side wires.

22. In a signaling charge device com using input terminals and output termina s, a condenser in circuit with said input terminals, two shunt paths about said condenser, one of said paths includin a high resistance.

23. n a signaling system, an electron discharge device comprising input terminals and output terminals, a condenser in circuit with said input terminals, two shunt paths about said condenser, each of said paths including a high resistance.

24. In a signaling system, the combination of an electron discharge device having an electron emitting cathode a cooperating anode and a grid for controlling the electron discharge, a condenser connected in circuit with said grid, a high resistance connected in shunt to said condenser, and a second high resistance in series with said shunt circult.

25. In a signalin system, a vacuum tube comprising a plura ity of electrodes, a condenser in shunt to said electrodes, two shunt paths about said condenser, each of said paths includin a high resistance.

26. In an e ectric system, an incomin line, a vacuum tube associated therewith an comprising an anode, a cathode, and a control electrode, a condenser in shunt to two of said electrodes and effectively in shunt to said line, and an aperiodic circuitcomprising said condenser.

27. In combination, an incoming line, means for amplifying signals impressed on said line, an inductance for inductively couling said means to said line, a condenser in circuit with said inductance and effectively in shunt to said line and the input terminals of said amplifying-means, and a resistance element in series with said inductance and said condenser.

28. A transmission system comprising a transformer, a vacuum tube repeater in circuit therewith and in close proximity thereto, and a wave form correcting device between sald transformer and said repeater, said device producing a substantial correction in wave forms over a wide range of frequencies.

29. A transmission system comprising a transformer, a vacuum tube repeater in circuit therewith, and a wave form correcting stem, an electron disdevice in circuit with said transformer and said re ater, said device producing a substantia correction in wave forms over a wide range of frequencies.

30. In combinatwn, a line, a repeater, an inductive coupling between said repeater and said line, said coupling transmitting with substantially equal attenuation all frequencies throughout a wide range of frequencies.

31. In an electric system, an incoming line, an outgoing line, a transformer between said lines, and localized means between said transformer and said outgoing line for substantially equalizing over a wide ran e of frequencies the unequal attenuation 0 said frequencies produced by said transformer.

32. In combination, a submarine cable, an artificial line for balancing said cable, said artificial line having one terminal grounded, a receiving device for receiving signals from said cable, a transmitting device for impressing out 0mg signals upon said cable a vacuum tu e amplifier between said cable and said receiving device, said vacuum tube having a plurality of electrodes. a connection to ground for one of said electrodes, and an inductive coupling between said tube and said line for preventing said last ound connection from short-circuiting sai artificial line.

33. In combination, a line, a repeater, a transformer therebetween, said transformer being less efficient for some frequencies of a range of frequencies to be transmitted than for other of said frequencies, and localized means for making the intensity of the currents in the secondary of said transformer independent of the frequency of the currents in the primary of said transformer for a wide range of frequencies.

34. A receiving system for signals, comprising a line, a transformer havin its rimary connected to said line, and a ocallzed correcting network connected to the secondary winding thereof, said network being composed of ohmic resistance and condensive reactance and being substantially free from inductive reactance.

35. In an electric system, two transmission lines, a transformer for connecting said lines, and a localized attenuation correcting means for a wide range of frequencies as sociated with said transformer, the electrical characteristics of said means being directly dependent upon the electrical characteristics of said transformer.

36. A signaling system comprising a line. a local receiving system for receiving signals from said line, said receiving system comprising means for producing a beneficial distortion in the signals received from said line. means for amplifying said distorted signals, and a transformer coupling between said line and said amplifying means.

37. The combination with a submarine cable of a responsive device for indicating the arrival of signaling current from said cable, means for amplifying the signals from said cable to a power value sufficient to actuate said indicating device, means for producing a beneficial change in the wave form of the arriving signals received from said cable prior to impressing them on said amplifying means, and an inductive coupling between said second recited means and said cable.

38. The combination with a signaling line of an electro-responsive device for receiving signals therefrom, means for amplifying said signals, means for producing a beneiicial change in the wave form of the arriving signals subsequent to receiving them from said line and prior to impressing them on said amplifying means, and a transformer coupling between said line and said amplif 'ing means.

39. ln electric system, comprising a line, a source of signals in said line, means for amplifying said signals and means comprising a symmetrically con-ducting aperiodic circuit between said line and said amplifying means for correcting for distortion in said signals produced prior to being received by said aperiodic circuit.

40. The combination with a transmission element in which the attenuation varies for different frequencies, of an auxiliary system connected to the terminals of said transmission element wherel'iy the resultant attenuation of the combined system will be substantially the same for each frequency over a wide range of frequencies, said auxiliary system comprising a network composed of ohmic resistance and condensive reactance and being substantially free from inductive reactance.

41. A receiving system for signals, comprising a wave form correcting network for a wide range of frequencies, said network being composed of ohmic resistance and condcnsive reactant-e and being substantially free from inductive rcactance.

42. A two-way repeating system between two lines, comprising means for repeating signals in one direction. means for repeating signals in the opposite direction. each of said means comprising a network for correcting for distortion in the arriving signals over a wide range of frequencies. said network being composed of ohmic resistance and condensive reactance, and being substantially free from inductive reactance.

43. The combination of a transmission device through which different frequencies are transmitted with different attennations. and an attenuation equalizer for said device con nectcd to the terminals thereof and comprising a network whose elements are so related to each other and to said device and so proportioned that all frequencies within a wide range are transmitted through said device and attenuation equalizer with substantially the same attenuation for each frequency.

44. The combination with a transmission element in which the attenuation varies with different frequencies of a lumped network connected to the terminals of said transmission element for making the resultant attenuation of the combined network and element substantially the same for each frequency over a wide range of frequencies.

45. The combination with a transmission element in which the attenuation varies with different frequencies, of an auxiliary system associated with the terminal of said transmission element, whereby the result ant attenuation of the combined system will be substantially the same for each frequency over a wide range of frequencies.

46. The combination with a transmission element in which the attenuation varies with different frequencies of a localized network connected to one end of said element for receiving currents from said element, said network comprising a lumped resistance and a lumped capacity connected to and terminating said transmission element of such values that the resultant attenuation of the combined system is substantially the same for each frequency over a wide range of frequencies.

47. The combination with a transmission element in which the attenuation varies with different frequencies of a localized network connected to one end of said element and terminating the same for receiving currents from said element, said network comprising electrical elements of such values that the resultant attenuation of the combined network and element is substantiallv the same for each frequency over a wide range of frequencies and means for amplifying said equally attenuated currents.

48. The combination of a signaling line and a localized receiving system for signals from said line comprising means for transmitting the component parts of the signals with equal attenuation over a wide range of frequencies. said means comprising a differ entiating device and an integrating device. and means for amplifying said equally attenuated signals.

49. The combination of two line sections and a localized two-way repeating system between said line sections, comprising means for repeating signals in one direction. means for repeating signals in the oppo ite dircc tion. each of said repeating means comprising means for transmitting the component parts of the signals with equal attenuation over a wide range of frequencies. said transmitting means comprising a diff rentiating device and an integrating device. and means for amplifying said equally attenuated signals.

local transmission circuit for receiving irom said line signaling currents of different frequency components and an electric device responsive to the currents in said transmission circuit, said transmission circuit comprising condensive and inductive reactances, and an ohmic resistance for eliminating the distortion of said currents due to said react ances.

52. A signaling system comprising a sending station, a' receiving station, a line conductor therebetween, a condenser, an inductance and a resistance in circuit with said line, said resistance having such a value as to substantially eliminate the distortion pro= duced by said condenser and inductance over a wide range of frequencies.

53. A system comprising cable terminals, a local two-way repeating system therebetween having apath for transmission in each direction of currents of different frequency com onents, each of said paths comprising con ensive and inductive reactances, and an ohmic resistance in circuit with said reactances and of such value as to substantially eliminate the distortion of said currents produced by said reactances.

54. In a transmission system, two transmission lines, a repeater system associated with said transmission line, said repeater system including two amplifying transmission paths, one for transmitting in one direction and the other for transmittin in the opposite direction, and a localize attenuation correcting means for equalizing the attenuation over a wide range of frequencies associated with the repeater system and said transmission line.

55. In a transmission system, two transmission lines, a repeater system between said lines, said system comprising a localized attenuation correcting means for equalizing the attenuation over a -Wi(l6 range of frequencies.

56. An electric system comprising two line sections, a balancing network for each of said line sections and a two-way repeating system between said sections, said repeating system comprising means for repeating signa s in one direction and means for repeating signals in the opposite direction, eachof said means comprising a correcting network composed of ohmic resistance and condensive reactance and being substantially free from inductive reactance.

57. In a transmission system, a transmission device, the attenuation in which varies with the frequenc an auxiliary system, the attenuation in w ich varies with the frequenc in a manner complemental to that of said evice so that the resultant transmission of said device and auxiliar system is substantially uniform for a wi e range of frequencies, and a repeater system associated with said device and auxiliary system.

58. In combination, a high resistance receiving circuit for electric waves, a vacuum tube having input terminals associated with said circuit, and means comprising a condenser in saidcircuit for substantially modifying the eifect of electrical impulses of short duration on said vacuum tube, said input terminals being connected across said condenser.

59. In combination, a highly damped circuit comprising a resistance of the order of several hundred thousands ohms, a vacuum tube having input terminals, connections between said circuit and said input terminals, and a condenser in shunt to said input terminals.

66. An incoming line, a vacuum tube, a transformer between said line and said tube, a condenser eii'ectively in shunt to said line and between said and a damping resistance element between said transformer and said tube.

61. A circuit including in series an inductance, a resistance, and a condenser, said resistance having such a value as to produce a substantial broadening of the tuning of said circuit, and a vacuum tube responsive to the dro in potential across the terminals of said condenser.

62. A circuit including in series an inductance, a resistance, and a condenser, said resistance having such a value as to produce a substantial broadening of the tuning of said circuit, and amplifying means responsive to the drop in potential across the terminals of said condenser.

63. The combination of a symmetrically conducting highly damped circuit, containing inductance and capacity, a vacuum tube having input terminals, an output circuit, and connections between said damped circuit and said input terminals.

64. In a signaling system, amplifying means'comprising input terminals and output terminals. a condenser, a transformer, a resistance element, a plurality of paths between said input terminals, one of said paths including said said paths including the secondary winding of said transformer.

said resistance being in series with the said condenser and secondary winding, and having such a value as to appreciably damp the circuit including said resistance, said condenser and the secondary winding of saidtransformer.

transformer and said tube,

condenser, another of 65. A highly damped signal receiving circuit, comprising a line adapted to receive incomin signals, a transformer connected to sakf line, a vacuum tube amplifier comprising cathode, anode and control electrodes, means for heating said cathode, a source of current between said cathode and anode, said cathode and control electrode being connected to respond to the potential supplied by the secondarywinding of said transformer, a resistance of the order of somei hundred thousand ohms in c rcuit with said transformer, and a condenser effectively in shunt to the line connecting the secondary winding of said transformer and said cathode and control electrode.

66. An electric circuit comprising an electron discharge device having a cathode, an anode, anda control electrode, 'an input circuit comprising said'cathode and control electrode. an output circuit comprising said cathode and anode, and a ground connec tion providing a leak path for direct current between ground and all of said electrodes for preventing a portion of the output current of said device from being impressed back on the input circuit of said device.

67. The method of signaling over a sub marine cable terminating at one end in an electroresponsive device, which comprises impressing low frequency telegraph impulses upon said cables at one end thereof, inductively impressing the signals received at the other end of said cable upon said device while preventing a substantial distortion of the signals as they occur in said cable, and amplifying said impulses prior to impressing them upon said device.

68. The method of transmitting currents over a wide range of frequencies between two line sections, which comprises inductively transmitting such currents from one line to an intermediate circuit, controlling the relative efiiciencv at which said frequencies are transmitte to prevent substantial distortion in said first step, amplifying said currents and impressing said amplified currents on the second line.

69. The method of transmitting currents between two line sections. which comprises connecting one of said lines to an intermediate circuit through a transformer, producing in the secondary of said transformer 11 current substantially proportional to the electromotive force in the primary of said transformer over a wide range of frequencies, amplifying said currents and impress- 1iug said amplified currents on the second 70. The method of transmitting currents over a wide range of frequencies between two line sections, which comprises inductively transmitting said currents from one line to an intermediate circuit, controlling the relative elliciency at which said frequencies are transmitted in said first step to produce a substantial equality of transmission thereof, amplifying said currents and impressing said amplified currents on the sec 0nd line.

7l The method of signaling over a submarine cable in which a vacuum tube amplifier is employed beneath thc'cable and an elcctroresponsive device, which comprises impressing low frequency telegraph impulscsupon said cable, inductively impresing said impulses uponIsaid' amplifier while preventing a substantial distortion of said signals as they occur in said cable, and impressing the amplified signals upon said device. a

72. In an electric system, means for translating short current impulses occuring at intervals into currents of longer duration than said impulses, said means comprising a circuit for said currents containing a resistance and a condenser in series, and a three electrode discharge device havin its input terminals connected to the terminals of said condenser through paths of low impedance.

73. The combination of a line, means for supplying impulses thereto, a receivin circult, a transformer for coupling sai line to said circuit, a high resistance, and means in circuit with said high resistance and adapted to be energized by said im ulses for actuating said receiving circuit urin a steady condition of the current in the primary of said transformer.

74. In a two-way repeating system for signals. two lines, means for supplyin low frequency impulses to said lines, a pat? for repeating signals in one direction between said lines, a path for repeating signals in the opposite direction between said lines, each of said paths comprising amplifying apparatus for said signals, a transformer for coupling one of said lines to said amplifying apparatus, a high resistance and means in circuit with said high resistance and effectively in shunt to one of said lines and adapted to be energized by said impulses for actuating said amplifying apparatus during a steady condition of the current in the primary of said transformer.

75. A two-wa repeating system comprising a path or repeating in one direction and a path for repeating in the opposite direction, one of said paths comprising an electrical discharge device having a cathode and another electrode, a source of voltage, and a connection to ground from a terminal of said cathode including said source.

76, In an electric s stem, an inoo line and an out oin inc, means comprising a vacuum tu e or impressing on said out oin line amplified waves'of substantial y t e same form as those receiyed by said tube from said incoming line, said tube comprising an anode, a cathode and a control electrode, said control electrode being associated with said incoming line, said anode being associated with said outgo ng line, a source of voltage, and a connection to ground from a terminal of one of said electrodes including said source.

77 In combination two line sections, a twoway repeating system therebetween comprising a vacuum tube amplifier having an input electrode, a cathode electrode and l an output electrode, means for impressin 15 signals from one of said lines upon said input electrode, a connection from said output electrode to the other line section, a source of voltage, and a connection to ground from an external terminal of one 20 of said electrodes through said source.

In witness whereof, I hereunto subscribe my name this 15th day of February, A: D., 1917.

BURTON W. KENDALL.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,453,982 granted May 1, 1923, upon the application of Burton W. Kenda'll, of New York, N. for an improvement in Electrical Receiving or Repeating TApparatus and Methods of Operating the Same, an error appears in the rinted specification requiring correction as follows: Pa 9, line 75, claim 71, or the word beneath read between; and that the said tters Patent should be read with this correction therein that the some mag conform to the record of the case in the Patent Oflice. igned and sealed this 19th day of June, A. D., 1923.

[mu] WM. A. KINNAN,

Acting Commissioner of Patents. 

